1. Field of the Invention
The invention relates to portable flameless heating apparatuses and methods utilizing an exothermic chemical reaction to produce heat without the need for an external source of energy such as a fire or flame. Particularly, there is disclosed hereby a flameless heater based on the exothermic reaction of a magnesium-iron alloy in the presence of salt and water, which apparatus generates sufficient energy to heat an item, material or component, as an example, but not limited to, a meal, a beverage, or any other item for consumer, industrial and military markets. Specifically, this disclosure relates to a flameless heater apparatus and method whose heating capacity and performance can be selected and tuned at the time of manufacture, and which is easily used and has a long shelf life.
2. Background Art
The use of magnesium-iron super-corroding alloy to design flameless heaters has been known for several decades. In the presence of an activator such as salt, a super-corroding alloy, typically a magnesium-iron alloy reacts with water, resulting in an exothermic reaction which generates heat and evolves hydrogen gas. It is possible to design a heating apparatus which is portable, safe to store and transport, and convenient to use. A number of such portable flameless heaters, particularly for heating of food, are known.
For example, a flameless ration heater pad based on the magnesium-iron alloy is described in U.S. Pat. No. 4,522,190 to Kuhn, et al., the disclosure of which is incorporated herein by reference. Kuhn, et al. describe a flameless ration heater pad or cake which consists of a super-corroding metallic alloy such as magnesium-iron and other ingredients blended together and dispersed throughout a porous matrix of polymeric material, such as polyethylene. When such a pad is wetted with saline water, an exothermic reaction is initiated, releasing enough energy to heat a desired substance. The magnesium-iron alloy used by Kuhn et al. contained 5 atomic percent (10.8 weight percent) iron.
Another example of a flameless ration heater based on magnesium-iron alloy is described in U.S. Pat. No. 5,611,329 to Lamensdorf, the disclosure of which is incorporated herein by reference. Lamensdorf teaches about a flameless ration heater made by first creating a mixture of magnesium-iron alloy powder with salt and an anti-foaming agent. Next, the blended powder is evenly distributed and enclosed into pockets made by selective thermal bonding of two rectangular non-woven gas and water permeable plastic sheets.
Other references providing useful background include U.S. Pat. No. 6,248,257 to Bell et al., and U.S. Pat. No. 7,258,117 to Payen et al., both of which are incorporated herein by reference.
Such flameless ration heaters can be included into a device specially created for a particular use, such as for heating a single or multiple serving meal or beverage or any other application.